Electricity has arrived as a fuel source for an increasing number of vehicles. Will this increase or decrease climate pollution compared to using gasoline?

I've heard so much confusion about this that I decided to make one of my Visual Carbon charts to allow informed comparisons at a glance. Turns out this was easier imagined than done. Determining the climate pollution from electric-fuelled vehicles requires compiling data on three new variables:

ELECTRICITY: The amount of climate pollution released when generating electricity varies dramatically between regions. This is the primary factor determining how much climate pollution an electric vehicle causes. MAKING THE CARS: Making electric cars and their batteries is significantly different than making old-school gasoline cars. Studies show that the climate pollution is higher to make electric vehicles. BATTERY REPLACEMENT: The climate impact of replacing traction batteries during the lifespan of an electric car needs to be considered.

After two weeks of dissecting geeky studies, wading through energy databases and hunting through industry websites I found what I needed.